1. Field of the Invention
The present invention relates to a capsule medical device guidance system that guides a capsule medical device introduced into a subject.
2. Description of the Related Art
In the field of endoscope, capsule medical devices equipped with an imaging function and a radio communication function inside a capsule-shaped casing formed into a size introducible into a digestive tract of a subject such as a patient have been known. After being swallowed through the mouth of a subject, a capsule medical device moves through the digestive tract by dint of peristaltic movement or the like. In the period between the time when such a capsule medical device is introduced into the digestive tract of a subject and the time when the capsule medical device is discharged out of the subject, the capsule medical device successively acquires images inside organs (hereinafter, may be referred to as in-vivo images) of the subject and wirelessly transmits the acquired in-vivo images to a receiving device outside the subject.
Each in-vivo image captured by such a capsule medical device is loaded into an image display device via the receiving device. The image display device displays each captured in-vivo image in a display as a still image or a moving image. A user such as a physician or a nurse observes each in-vivo image of the subject displayed in the image display device to make an examination inside an organ of the subject through the observation of each in-vivo image.
On the other hand, in recent years, capsule medical device guidance systems that guide a capsule medical device inside a subject by a magnetic force (hereinafter, referred to as magnetic guidance) are proposed. Generally in a capsule medical device guidance system, a capsule medical device is further equipped with a permanent magnet inside a capsule-shaped casing and an image display device displays each in-vivo image successively captured by the capsule medical device inside a subject in real time. The capsule medical device guidance system applies a magnetic field to the capsule medical device inside the subject to magnetically guide the capsule medical device inside the subject to a desired position by a magnetic force of the applied magnetic field. A user operates magnetic guidance of the capsule medical device by using an operation unit of the capsule medical device guidance system while referring to an in-vivo image displayed in the image display device.
Among such capsule endoscopes, a capsule endoscope that has a specific gravity floatable in a liquid introduced into an organ to make an observation inside such a relatively large-space organ such as the stomach or large intestine and successively captures in-vivo images while floating in the liquid is known. And there is a case when a subject is made to take in a liquid to expand the inside of an organ (more specifically, a wall of an organ inner wall) to make a concentrated examination inside such a relatively large-space organ such as the stomach and a capsule endoscope having a specific gravity smaller than that of the liquid (see, for example, WO 2007/077922). In this case, the capsule endoscope successively captures images inside the organ expanded by the liquid while floating in the liquid in a mode to take a predetermined posture (for example, a vertical posture in which the center axis of the capsule endoscope in a longitudinal direction and the liquid surface are substantially perpendicular) inside the organ such as the stomach. Such a capsule endoscope can capture images in a wider range inside the organ by moving in a desired direction while floating in the liquid inside the organ.